Add docs

src/third_party_setup/avian/collision_layer.rs

@@ -10,14 +10,22 @@ pub(super) fn plugin(app: &mut App) {
 
 #[derive(PhysicsLayer, Default)]
 pub enum CollisionLayer {
+    /// Any [`RigidBody::Static`] collider that does not have an explicit layer will default to `Terrain`.
+    /// This is used for e.g. the ground, trees, benches, buildings, etc.
     #[default]
     Terrain,
-    Player,
+    /// A character is any entity that can move around and interact with the environment.
     Character,
+    /// The player character.
+    Player,
+    /// A prop is a [`RigidBody::Dynamic`] collider, i.e. it can be influenced by physics.
     Prop,
+    /// A [`Sensor`] that detects the presence of a player in order to allow the player to initiate dialogue.
     DialogSensor,
 }
 
+/// A way to easily override the default collision layer in Blender.
+/// Does not include `Terrain` because that one is already the default.
 #[derive(Debug, Clone, Copy, Reflect, PartialEq, Eq)]
 #[reflect(Debug, PartialEq, Component)]
 pub enum CollisionLayerPreset {
@@ -31,15 +39,18 @@ impl From<CollisionLayerPreset> for CollisionLayers {
     fn from(preset: CollisionLayerPreset) -> Self {
         use CollisionLayer::*;
         match preset {
+            // A player is both a character and a player. They can interact pretty much everything.
             CollisionLayerPreset::Player => CollisionLayers::new(
                 [Player, Character],
                 [Terrain, Character, Prop, DialogSensor],
             ),
+            // NPCs are just characters. They cannot interact with sensors in this case.
             CollisionLayerPreset::Npc => {
                 CollisionLayers::new([Character], [Terrain, Character, Prop])
             }
-            // Since in our example our only sen
+            // Dialog sensors can only interact with players.
             CollisionLayerPreset::DialogSensor => CollisionLayers::new(DialogSensor, Player),
+            // Props can interact with terrain, other props, and characters.
             CollisionLayerPreset::Prop => CollisionLayers::new(Prop, [Terrain, Prop, Character]),
         }
     }